Assessing the influence of rice roots and root exudates on nitrogen mineralization using a novel protocol

Classical nitrogen (N) mineralization experiments are done using uncropped soil, thus completely neglecting the influence of roots and root exudates. Therefore, experiments were conducted at two field sites in Bangladesh during ‘boro’ season (winter rice), using two rice cultivars (BRRI Dhan 29 and BINA Dhan6) to investigate the influence of rice roots and root exudates on N mineralization. Rice cultivars were transplanted in three replicated plots maintaining 25 x 15cm spacing along with three replicated uncropped plots as control. A novel method was used to identify the most suitable location to assess N mineralization in soil having actively growing rice plants. For this purpose, soil samples were collected from three locations in soil namely; 1) rhizosphere (0cm, at the rhizosphere), 2) middle of the two plants (7.5cm apart from rhizosphere) and 3) middle of two rows (12.5cm apart from rhizosphere). There was significant stimulatory effect of rice roots and root exudates on N mineralization at both filed sites. Significant influences of rice varieties were also observed, with BINA Dhan 6 having greater influence on N mineralization than BRRI Dhan 29. Sampling location also had a significant effect on measured N mineralization. The highest stimulatory effects of rice roots and root exudates were recorded when soil was sampled from rhizosphere. Sampling between the plants and between the rows had similar effects. In conclusion, rice roots and root exudates had a large influence on N mineralization and the best sampling location to determine the effects of actively growing rice roots and root exudates on N mineralization, was the rice rhizosphere

Shifts in soil organic matter composition following treatment with sodium hypochlorite and hydrofluoric acid

A renewed interest in chemical fractionation of soil organic matter (SOM) originates from the premise that it enables to isolate labile SOM from SOM protected through mineral binding and recalcitrant SOM. Both selective removal of labile non-bound SOM through oxidation or hydrolysis as well as selective removal of minerals and attached SOM are often applied. Molecular-level SOM characterization by means of temperature resolved Pyrolysis-Field Ionization Mass Spectroscopy analysis (Py-FIMS) was used here as an approach to obtain insight into the fate of SOMuponwet chemical treatment with regard to composition and thermal stability. The applied sequential chemical treatment with 6% NaOCl and 10% HF yielded similar sizes in stable SOM fractions between sandy semi-native heathland and cultivated cropland soil pairs (i.e. NaOCl resistant OC: 12.3–15.0 g C kg−1 and NaOCl+HF resistant OC: 2.6–5.3 g C kg−1). Py-FIMS spectra of bulk SOM in both heathland–cropland soil pairs were dominated by signals assigned to lipids, alkylaromatics and sterols. Difference spectra and thermograms showed selective loss of signals from sterols, lignin dimers and thermolabile lipids. This matches advancing SOM decomposition as derived from previously reported gradients in SOM composition as decomposition proceeds fromplantmaterial over particulate organicmatter (OM) to SOMin silt and clay particle sizes. However, increased ion intensity attributed to carbohydrates, peptides and short-chained lipids after NaOCl treatment indicates that biologically labile SOM components were also enriched, and they may possibly have been protected through mineral binding or encapsulation in macromolecular OMstructures. Subsequent HF treatment yielded increased volatilization in the thermostable region for mass signals tentatively assigned to phenols and lignin monomers and of heterocyclic N-containing compounds and thermostable alkylaromatics. The resistance to chemical treatment of the latter two components matches with their hypothesized structural function in macro OM molecules. However, even for the sites investigated here, with a very similar soil texture, climate, land-use, drainage and contents of pedogenic oxides, contrasting and not readily explainable results were found for other SOMconstituents. Therefore, chemical fractionations seemto yield very site specific and less distinct patterns and this study demonstrated that derivation of useful information regarding SOM stabilization mechanisms from such experiments is by no means straightforward

Nonlinear Stress Fluctuation Dynamics of Sheared Disordered Wet Foam

Sheared wet foam, which stores elastic energy in bubble deformations, relaxes stress through bubble rearrangements. The intermittency of bubble rearrangements in foam leads to effectively stochastic drops in stress that are followed by periods of elastic increase. We investigate global characteristics of highly disordered foams over three decades of strain rate and almost two decades of system size. We characterize the behavior using a range of measures: average stress, distribution of stress drops, rate of stress drops, and a normalized fluctuation intensity. There is essentially no dependence on system size. As a function of strain rate, there is a change in behavior around shear rates of $0.07 {\rm s^{-1}}$.Comment: accepted to Physical Review

Combined application of foliar fertilizer with basal NPK enhances mulberry leaf yield and silkworm cocoon productivity in calcareous soil

One of the reason of low Mulberry plant (Morus spp.) production in calcareous soils is due to the low efficiency of soil applied fertilizers. Thus, in search of an alternative efficient fertilizer application method, field experiments were conducted at Bangladesh Sericulture Research and Training Institute (BSTRI), Rajshahi, Bangladesh in consecutive two years for achieving higher productivity of mulberry leaf and silkworm cocoon, Bombyx mori L. Four fertilizer management practices such as Control, Basal, Basal + Urea (B+U) and Basal + Foliar fertilizer (FF) were followed for mulberry plant production. Result showed that 3 times FF spray with basal application of NPK (305 kg N, 105 kg K and 66 kg P ha-1 yr-1 in 4 splits doses enhances biochemical constituents in mulberry leaf, leaf yield, silkworm growth as well as cocoon parameters. This study concluded that this treatment was regarded as the best fertilizer management practice which increased the mulberry leaf and cocoon productivity by 17.0 and 52.8 %, respectively over the control. Leaf quality of mulberry in terms of moisture, crude protein, soluble carbohydrate, reducing sugar and total mineral was increased by 14.0, 57.6, 85.8, 140.4 and 60.5 %, respectively in comparison with the control. Thus, foliar spray of foliar fertilizer had a good impact on sericultural productivity

Post-harvest quality of fresh-marketed tomatoes as a function of harvest periods

Losses on tomato business chain start at harvest, a two-months period. At the beginning of the harvest, fruits concentrate at the basal part of the plant, then in the middle, and finally at the top, and undergo changes in diameter and maturity indexes as harvest progresses. The aim of this work was to evaluate the impact of handling at three different periods: (I) 15 days, (II) 30 days, and (III) 45 days after the beginning of harvest. Tomatoes were ordinarily grown and harvested in to bamboo baskets, and transferred to plastics boxes. Fruits were classified according to ripening stage and diameter, and evaluated for mechanical damage and external defects caused by harvesting procedures. The time required for the harvest operation was measured; damage to fruits (%) and weight loss (%), caused either in the field and/or during the harvesting process, were taken into consideration and related to the final quality of fruit after storage for 21 days. The same methodology was used all through the production and harvest cycle. The highest % fruit damage occurred during period II, a longer harvest time than the other two periods. Fruits not submitted to handling showed lower weight loss than handled fruits. Fruits harvested in period II and stored for 21 days showed higher losses due to mechanical injury

A STUDY ON SEROPREVELENCE AND RISK FACTORS OF BOVINE LEPTOSPIROSIS IN LOWER ASSAM, INDIA

The present study was conducted to ascertain the seroprevalence of Leptospira infection in cattle among certain districts of the lower Brahmaputra valley in the state of Assam from March 2017 to February 2018. Two serological tests viz. IgG ELISA and Microscopic Agglutination Test (MAT) were used to detect the leptospiral antibodies. The anti-leptospiral antibodies were detected by IgG ELISA and compared with MAT using antigens from 12 pathogenic serovars. Out of 380 sera samples, 68 (17.89 %, 95% CI: 6.89-27) and 44 (11.58%) were positive by IgG ELISA and MAT respectively. The circulating Leptospira serovars identified were Autumnalis (6.05%), Ballum (2.63%), Batavia (1.31%), Ichterohaemorrhagie (0.7%), Javanica (0.5%) and Sejroe (0.2%). The sensitivity and specificity of IgG ELISA in comparison to MAT were calculated and found to be 100% and 92.85% respectively with a concordance of 93.68%. An epidemiological investigation was carried out to find the association of various risk factors with Leptospira infection under this study in cattle using a pre-tested questionnaire. The present study will serve as baseline data for the prevention and control of Leptospira infection in cattle

Strawberry fruit resistance to simulated handling

Harvest operations are currently the main source of mechanical injury of strawberry (Fragaria x ananassa Duch.). Experiments were designed to simulate conditions encountered during commercial handling. Individual fruits were subjected to impact or compression forces with similar energy to determine the sensitivity to mechanical injury. Bruise volume was used as the measurement of injury. Bruise severity increased as a function of impact energy for both impact types. However, dropped fruits had larger bruise volume than fruits submitted to pendulum impactor at the same energy level. Doubling the impact energy (0.040 to 0.083 J) increased bruise volume by 7 times (13 to 91 mm³). Fruits dropped from 380 mm (0.075 J) showed 71% greater bruise volume than those dropped from either 130 mm (0.025 J) or 200 mm (0.040 J). Compressed fruits showed higher bruise volume than other tests. Some cultivars are more susceptible to compression forces than others. 'Sweet Charlie' berries showed bruise volume 40% higher than the others cultivars when subjected to compression. Fruits subjected to impact showed bruise volume lower than the compressed fruits, indicating the possibility to be handled and graded in a packing line.A etapa de colheita é a principal fonte de danos físicos ao morango (Fragaria x ananassa Duch.). Experimentos foram realizados para simular condições encontradas durante manuseio. Frutos foram submetidos individualmente às forças de impacto e compressão em energias similares para determinar sensibilidade dos frutos a danos físicos. Volume da injúria física foi utilizado para mensurar a incidência do dano físico ocorrido. Severidade da lesão aumenta, com incremento da energia, tanto para força de impacto como para compressão. Todavia, frutos submetidos à queda livre demonstraram maiores volumes de danos físicos do que frutos submetidos a danos ocasionados por pendulo no mesmo nível de energia. Dobrando a energia de impacto (0,040 para 0,083 J) ocorreu aumento no volume da injúria em sete vezes (13 para 91 mm³). Frutos submetidos à queda de 380 mm (0,075 J) demonstraram volumes de danos físicos 71% superiores do que aqueles ocasionados em queda de 130 mm (0,025 J) ou 200 mm (0,040 J). Frutos em teste de compressão mostraram maiores volumes de injúrias físicas do que outros testes. Alguns cultivares são mais sensíveis à força de compressão do que outros. Frutos cultivar 'Sweet Charlie' apresentaram volume de injúria 40% superiores do que outros quando submetidos à força de compressão. Morangos submetidos à força de impacto demonstraram volume de injúria inferior do que aqueles comprimidos, indicando a possibilidade dos morangos serem classificados e manuseados em uma linha de beneficiamento